//SamXIAO
#include <bits/stdc++.h>
using namespace std;
#define PI 3.1415926
#define   SQUARE(x) ((x)*(x))
//double SQUARE(double x) { return x*x;}
#define N_MAX 987654321
#define N_MIN -N_MAX
int f[286];
char s1[1086];
char s2[2020];
void w1()
{
	int cnt = 0, ans = 0;
	float req;
	scanf("%f", &req);
	scanf("%s%s", s1, s2);
	for(int i =0; i<strlen(s1); i++)
		if(s1[i] == s2[i]) cnt++;

	printf("%s", req <= cnt/(float)strlen(s1) ? "yes" : "no");
}

int main()
{
	w1();
  return 0;
}
